1. Field of the Invention
The present invention relates to a high-speed shear with a knife, particularly a chisel-type knife with a knife edge, arranged on at least one of two oppositely arranged drums, wherein the knife can be accelerated to the feeding speed of the rolled strip and the drums can be adjusted relative to each other for carrying out a cut. At least one drive unit provided for the drums serves to accelerate the drums to the speed of the rolled strip to be cut and at least one of the drums may be provided with a separately controllable adjusting device.
2. Description of the Related Art
In the manufacture of hot-rolled wide strip, the endless rolling method is used more and more. The material used is produced by welding preliminary strips or in casting machines. However, hot-rolled wide strip is also manufactured by using a semi-endless rolling method in which the material used may have the length of several preliminary strips which may be stored intermediately on roller tables, roller-hearth furnaces or in coil boxes.
After the hot-rolling procedure, the finished strip must be cut to the strip lengths corresponding to the required coil weights. The cut should be carried out in a continuous operation, i.e., at rolling speed. Accordingly, the cut must be carried out at the speeds of trains for hot-rolling wide strip which are conventional today in the range of 5 m/sec. to 30 m/sec., preferably 10 m/sec. to 20 m/sec. The strip thicknesses are between 0.5 mm to 30 mm, preferably between 0.6 mm to 1.5 mm.
Rotary shears or guillotine shears which are conventional in the art and serve to cut hot-rolled wide strip, are not designed for such high strip speeds. However, flying shears which are used following cold-rolling tandem trains usually operate today only at strip speeds of about 6 m/sec; in these type of shears there is also a demand for significantly higher speeds.
At such high strip speeds, it is no longer possible to economically carry out the conventional cutting procedures in which the knife drum is accelerated to a strip speed of up to 30 m/sec. for carrying out the cut and in which the knife drum must subsequently be decelerated again.
In order to eliminate these difficulties, it has already been proposed to control the acceleration of the knife drum to strip speed or the operation of the knife drum at strip speed separate of the movement to be carried out perpendicularly of the strip and to provide for at least one of the drums a separately controllable adjusting device.
In this connection, it is possible to provide one of the drums with a knife and the other drum with an anvil or a surface portion acting as an anvil which interacts with the knife.
However, when the shear has this configuration, a safe and exact cut can only be ensured if the cutting gap between the knife cutting edge and the anvil or the surface portion of the counter-drum is zero. If this is not the case, for example, if the knife has an excess length, the knife and the anvil may be overloaded until they are destroyed, or when the knife has an insufficient length the cut remains incomplete.
However, due to one or more interacting variables including thermal extension, wear, elastic behavior of the adjusting devices, acceleration forces, finishing tolerances, etc. the adjustment of the cutting gap to “zero” cannot be achieved with the required certainty. Therefore, it is necessary for a certain and reliable cutting of the strip that the knife protrudes from the cutting circle. However, this protrusion leads to a rapid increase of the cutting forces and, thus, to wear phenomena in all structural components of the cutting elements, the adjusting device and the bearings of the drums.